A multi-scale heterogeneous nano-structured high-strength high-plasticity 201 stainless steel and a preparation method thereof

Abstract

This invention discloses a multi-scale heterogeneous nanostructured high-strength and high-ductility 201 stainless steel and its preparation method, belonging to the field of metal material preparation technology. Without altering the basic composition of 201 stainless steel, this invention employs a complete thermomechanical treatment process of solution treatment, warm rolling, cold rolling, and annealing to construct a multi-scale heterogeneous nanostructure containing nanoscale deformed laths, submicron-scale recrystallized grains, and micron-scale non-recrystallized grains, forming an austenite / martensite dual-phase matrix. Relying on the synergistic effect of multiple mechanisms such as heterogeneous deformation-induced strengthening, TRIP phase transformation plasticization, and grain refinement strengthening, it breaks through the traditional limitation of the inversion of strength and plasticity in materials, achieving an excellent balance of strength and plasticity. This invention features a simple process, is suitable for applications in construction, transportation, and medical devices, and has promising prospects for industrial application.

Description

Technical Field

[0001] This invention relates to the field of metal material preparation technology, and in particular to a multi-scale heterogeneous nanostructured high-strength and high-ductility 201 stainless steel and its preparation method. Background Technology

[0002] The main components of commercial nickel-saving 201 stainless steel (by mass fraction) are: C < 0.2%, Ni 1.0%-2.0%, Cr 12.5%-15.5%, Mn 8.0%-11.0%, Si < 0.75%, N < 0.2%, and Cu < 1.0%. This material boasts advantages such as low cost, excellent corrosion resistance, and good formability. However, its yield strength is generally less than 500 MPa, making it unsuitable for applications requiring high load-bearing capacity, lightweight construction, and long fatigue life, which demand stringent mechanical properties. While traditional cold-rolling annealing processes can improve steel strength through work hardening and grain refinement, this increase in strength leads to a significant decrease in plasticity, making it difficult to achieve a good balance between strength and plasticity.

[0003] Current research has demonstrated significant strength enhancements in various steel grades through thermomechanical treatments such as large plastic deformation, warm rolling, and cryogenic rolling. For example, Li et al. achieved a tensile strength exceeding 2.2 GPa and a uniform elongation greater than 20% in medium-manganese steel using multiple transverse forging, cryogenic treatment, and tempering processes (Science, 2023, 379, 168-173). Geng et al. achieved a yield strength of 2977 MPa and a total elongation of 7.0% in martensitic aging steel through a high-temperature, intense plastic deformation combined with a multi-mismatched nano-coprecipitate strengthening strategy (Nature Communications, 2026, 17, 5352). However, these high-strength steels either contain expensive metallic elements (such as Co and Mo) or employ complex and difficult-to-scale large plastic deformation processes, and their corrosion resistance is inferior to that of stainless steel systems, limiting their widespread application.

[0004] Therefore, how to rely on the existing composition system, regulate the microstructure through thermomechanical treatment, improve its strength-plasticity matching relationship, and overcome the contradiction between the increase in strength and the decrease in plasticity in the existing technology is a technical problem that needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-scale heterogeneous nanostructure high-strength and high-ductility 201 stainless steel and its preparation method, so as to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention provides a method for preparing high-strength, high-ductility 201 stainless steel with a multi-scale heterogeneous nanostructure, comprising the following steps: S1. The hot-rolled 201 stainless steel slab is solution treated and then water-quenched to room temperature. S2. The solution-treated slab obtained in step S1 is subjected to multi-pass warm rolling at 400-550℃, with a total reduction rate of 25%-50% and a single-pass reduction rate of 10%-20%, to obtain warm-rolled strip. S3. The warm-rolled strip obtained in step S2 is subjected to room temperature multi-pass cold rolling with a total reduction rate of 15%-70% and a single-pass reduction rate of 5%-15% to obtain cold-rolled strip. S4. The cold-rolled strip obtained in step S3 is annealed at 650-950℃ for 0.5-10 min under a protective atmosphere at a heating rate of 3-10℃ / min, then cooled to below 400℃ at a cooling rate of 5-15℃ / min, and then air-cooled to room temperature to obtain the multi-scale heterogeneous nanostructured high-strength and high-plasticity 201 stainless steel.

[0007] Furthermore, in step S1, the solution treatment temperature is 950-1050℃ and the time is 0.5-2 h.

[0008] Further, in step S1, the chemical composition of the 201 stainless steel plate, by mass percentage, includes: C<0.2%, Ni1.0%-2.0%, Cr12.5%-15.5%, Mn8.0%-11.0%, Si<0.75%, N<0.2%, Cu<1.0%, with the balance being Fe and unavoidable impurities.

[0009] Furthermore, in step S2, the rolling speed of the multi-pass warm rolling is 1-5 m / s, and the rolling process uses a front tension of 100-200 MPa and a back tension of 80-150 MPa.

[0010] Furthermore, after step S4, the process further includes a step of leveling and rolling the strip obtained after annealing; the reduction rate of the leveling and rolling is 0.5%-3%. The purpose of the leveling and rolling is to eliminate the yield plateau effect.

[0011] Furthermore, in step S2, the temperature of the multi-pass warm rolling is 420-480℃, and the single-pass reduction rate is 12%-18%; in step S3, the total reduction rate of the room temperature multi-pass cold rolling is 20%-60%, and the single-pass reduction rate is 8%-12%.

[0012] Furthermore, in step S4, the annealing temperature is 680-850℃, the time is 0.5-8 min, and the cooling rate is 8-12℃ / min.

[0013] The present invention also provides a multi-scale heterogeneous nanostructured high-strength and high-plasticity 201 stainless steel prepared by the above preparation method.

[0014] Furthermore, the matrix structure of the multi-scale heterogeneous nanostructured high-strength and high-ductility 201 stainless steel consists of 40%-80% austenite and 20%-60% martensite by volume, and possesses the following multi-scale heterogeneous nanostructure: Nanoscale deformable slats with widths of 40-550 nm; Submicron-sized recrystallized grains, with a size of 0.5-1.5 μm and a volume fraction of 30%-60%; Micron-sized, non-recrystallized grains, ranging in size from 1 to 25 μm.

[0015] Furthermore, the yield strength of the multi-scale heterogeneous nanostructured high-strength and high-ductility 201 stainless steel is 1000-1300 MPa, the tensile strength is 1400-1600 MPa, and the total elongation is 25%-45%.

[0016] The present invention discloses the following technical effects: This invention, without altering the basic composition of existing nickel-saving 201 stainless steel, constructs a multi-scale heterogeneous nanostructure composed of nanoscale deformed laths, submicron-scale recrystallized grains, and micron-scale non-recrystallized grains, along with an austenitic / martensite dual-phase matrix, through a complete thermomechanical treatment process of solution treatment, warm rolling, cold rolling, and annealing. Relying on the synergistic effects of multiple mechanisms such as heterogeneous deformation-induced strengthening, TRIP phase transformation plasticization, and grain refinement strengthening, it effectively overcomes the limitation of the traditional inversion of strength and plasticity, achieving an excellent balance between strength and plasticity.

[0017] This invention utilizes all existing conventional rolling and annealing equipment in steel mills, requires no addition of expensive alloying elements, has a simple process, and has good prospects for industrial application. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The microstructure of the multi-scale heterogeneous nanostructure high-strength and high-ductility 201 stainless steel prepared in Example 1 of this invention is characterized by SEM-EBSD and HAADF-STEM. Among them, (a) is the inverse pole figure (IPF) distribution map, (b) is the phase distribution map, (c) is the DF-HAADF image, and (d) is the grain size distribution map.

[0020] Figure 2The X-ray diffraction (XRD) pattern of the high-strength and high-plasticity 201 stainless steel with multi-scale heterogeneous nanostructure prepared in Example 1 of the present invention.

[0021] Figure 3 The diagram shows a comparison of the engineering stress-strain curves of the multi-scale heterogeneous nanostructured high-strength and high-plasticity 201 stainless steel prepared in Examples 1-8 of this invention and the 201 stainless steel prepared in Comparative Examples 1-3.

[0022] Figure 4 This is a comparison chart of the mechanical properties of the multi-scale heterogeneous nanostructured high-strength and high-plasticity 201 stainless steel prepared in Example 3 of the present invention and the cold-rolled high-strength stainless steel prepared domestically and internationally under existing technologies.

[0023] Figure 5 The microstructure of the multi-scale heterogeneous nanostructure high-strength and high-ductility 201 stainless steel prepared in Example 2 of this invention is characterized by SEM-EBSD and HAADF-STEM. Among them, (a) is the inverse pole figure (IPF) distribution map, (b) is the phase distribution map, (c) is the DF-HAADF image, and (d) is the grain size distribution map.

[0024] Figure 6 The microstructure of the multi-scale heterogeneous nanostructure high-strength and high-ductility 201 stainless steel prepared in Example 3 of this invention is characterized by SEM-EBSD and HAADF-STEM. Among them, (a) is the inverse pole figure (IPF) surface distribution map, (b) is the phase distribution map, (c) is the DF-HAADF image, and (d) is the grain size distribution map.

[0025] Figure 7 The microstructure of the multi-scale heterogeneous nanostructure high-strength and high-ductility 201 stainless steel prepared in Example 4 of this invention is characterized by SEM-EBSD and HAADF-STEM. Among them, (a) is the inverse pole figure (IPF) distribution map, (b) is the phase distribution map, (c) is the DF-HAADF image, and (d) is the grain size distribution map.

[0026] Figure 8 The microstructure of the multi-scale heterogeneous nanostructure high-strength and high-ductility 201 stainless steel prepared in Example 5 of this invention is characterized by SEM-EBSD and HAADF-STEM. Among them, (a) is the inverse pole figure (IPF) plane distribution map, (b) is the phase distribution map, (c) is the DF-HAADF image, and (d) is the grain size distribution map.

[0027] Figure 9 The microstructure of the multi-scale heterogeneous nanostructure high-strength and high-ductility 201 stainless steel prepared in Example 6 of the present invention is characterized by SEM-EBSD; wherein, (a) is the inverse pole figure (IPF) distribution map, (b) is the phase distribution map, and (c) is the grain size distribution map.

[0028] Figure 10 The microstructure of the multi-scale heterogeneous nanostructure high-strength and high-ductility 201 stainless steel prepared in Example 7 of the present invention is characterized by SEM-EBSD; wherein, (a) is the inverse pole figure (IPF) distribution map, (b) is the phase distribution map, and (c) is the grain size distribution map.

[0029] Figure 11 The microstructure of the multi-scale heterogeneous nanostructure high-strength and high-ductility 201 stainless steel prepared in Example 8 of the present invention is characterized by SEM-EBSD; wherein, (a) is the inverse pole figure (IPF) distribution map, (b) is the phase distribution map, and (c) is the grain size distribution map.

[0030] Figure 12 The microstructure of the 201 stainless steel prepared in Comparative Example 4 of this invention is characterized by SEM-EBSD; wherein, (a) is the inverse pole figure (IPF) distribution map, (b) is the phase distribution map, and (c) is the grain size distribution map. Detailed Implementation

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0033] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0034] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0035] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0036] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0037] In this invention, room temperature refers to 20-25℃.

[0038] This invention provides a high-strength, high-plasticity, multi-scale heterogeneous nanostructured 201 stainless steel, the preferred preparation method of which includes the following steps: S1: Solution treatment Hot-rolled 201 stainless steel slabs with a thickness of 2.0-4.0 mm are solution treated at a temperature of 950-1050℃ for 0.5-2 hours, and then water-quenched to room temperature.

[0039] The chemical composition of the 201 stainless steel, by mass percentage, is: C<0.2%, Ni 1.0%-2.0%, Cr 12.5%-15.5%, Mn 8.0%-11.0%, Si<0.75%, N<0.2%, Cu<1.0%, with the balance being Fe and unavoidable impurities.

[0040] The purpose of solution treatment is to eliminate banded structures, carbide precipitates, and compositional segregation formed during hot rolling, ensuring that alloying elements such as Cr, Ni, Mn, and C are fully dissolved in the austenite matrix to obtain a uniform single-phase austenite structure. This provides a uniform initial state for microstructure control during subsequent warm rolling. Below 950℃, carbide dissolution is incomplete, and residual carbides become crack initiation sources during subsequent deformation; above 1050℃, grain coarsening is severe, reducing the strength of the final product. Insufficient holding time leads to incomplete solution treatment, while excessive holding time wastes energy and may cause abnormal grain growth. Water quenching aims to quickly pass through the carbide precipitation temperature range, suppressing Cr precipitation during cooling. 23 The precipitation of carbides such as C6 maintains a supersaturated solid solution state.

[0041] S2: Multi-pass warm rolling The solution-treated slab obtained in step S1 is subjected to multi-pass warm rolling at a rolling temperature of 400-550℃, a total reduction rate of 25%-50%, a single-pass reduction rate of 10%-20%, and a rolling speed of 1-5 m / s. During the rolling process, a front tension of 100-200 MPa and a back tension of 80-150 MPa are used to obtain a warm-rolled strip with a thickness of 1.0-3.0 mm.

[0042] Warm rolling is one of the key steps in constructing the multi-scale heterogeneous nanostructure in this invention. Within the temperature range of 400-550℃, 201 stainless steel is in a critical state between dynamic recovery and partial dynamic recrystallization: on the one hand, the higher temperature promotes dislocation cross-slip and climb, avoiding the work hardening saturation caused by the large-scale dislocation entanglement during room temperature cold rolling; on the other hand, the solid solution dragging effect of Mn and N elements and the pinning effect of Cr carbides inhibit the occurrence of complete dynamic recrystallization, allowing the microstructure to retain some unrecrystallized regions. This partially recrystallized microstructure lays the foundation for the formation of heterogeneous grain structures during subsequent room temperature cold rolling and annealing.

[0043] The synergistic effect of the initial tension of 100-200 MPa and the subsequent tension of 80-150 MPa is that tension not only helps control the sheet shape, but more importantly, it promotes dislocation multiplication and subgrain boundary formation within the grains. Simultaneously, the tension-induced additional shear stress helps activate more slip systems, resulting in more uniform deformation and reducing the risk of edge cracking. A total reduction rate of 25%-50% ensures sufficient cumulative strain to refine the grains while preserving deformation space for subsequent cold rolling.

[0044] S3: Room temperature multi-pass cold rolling The warm-rolled strip obtained in step S2 is subjected to room temperature multi-pass cold rolling with a total reduction rate of 15%-70% and a single-pass reduction rate of 5%-15% to obtain a cold-rolled strip with a thickness of 0.7-2.0 mm.

[0045] Room temperature cold rolling introduces a high density of dislocations on top of the partially recrystallized structure formed by warm rolling. Compared to direct room temperature cold rolling from the solution state, the structure after warm rolling has a more uniform dislocation distribution and finer initial grains. Therefore, subsequent cold rolling can achieve a larger cumulative reduction rate without causing edge cracking. The single-pass reduction rate is controlled at 5%-15% to avoid local stress concentration and edge cracking caused by excessive deformation in a single pass. In this step, due to the low stacking fault energy of 201 stainless steel (approximately 14-25 mJ / m²), martensitic phase transformation (ε-martensite and α'-martensite) is easily induced during deformation, forming an austenite-martensite dual-phase structure, which provides the driving force for the reverse phase transformation and recrystallization in subsequent annealing.

[0046] S4: Annealing treatment The cold-rolled strip obtained in step S3 is annealed at a temperature of 650-950℃, a heating rate of 3-10℃ / min, a holding time of 0.5-10 min, and a protective atmosphere of N2. Then it is cooled to below 400℃ at a rate of 5-15℃ / min and then air-cooled to room temperature.

[0047] Annealing is the core step in achieving the "multi-scale heterogeneous nanostructure" of this invention. Within a temperature range of 650-950℃, the cold-rolled microstructure undergoes multiple processes including recovery, recrystallization, and reverse phase transformation: some high-energy regions (such as martensite lath boundaries and high-density dislocation regions) preferentially recrystallize, forming submicron-sized equiaxed grains; while some low-energy regions or incompletely recrystallized regions retain deformed microstructure characteristics, forming nanoscale deformed laths and micron-sized unrecrystallized grains. Controlling the heating rate (3-10℃ / min) is crucial: an excessively fast heating rate leads to uneven microstructure transformation and the formation of coarse grains; an excessively slow heating rate results in an overly thorough recovery process, consuming the recrystallization driving force and hindering fine grain formation. A holding time of 0.5-10 min ensures sufficient recrystallization while preventing excessive grain growth.

[0048] During annealing, controlling the cooling rate of 5-15℃ / min is equally crucial: a suitable cooling rate during the cooling process from the annealing temperature to 400℃ avoids residual stress caused by excessively rapid cooling while suppressing Cr degradation caused by excessively slow cooling. 23 The coarse precipitation of C6 carbides. The N2 protective atmosphere prevents surface oxidation and nitriding at high temperatures, ensuring surface quality.

[0049] In a preferred embodiment, the warm rolling temperature in step S2 is 420-480°C, and the single-pass reduction rate is 12%-18%. This temperature range is closer to the lower limit of the dynamic recrystallization temperature of 201 stainless steel, which is beneficial for obtaining a finer partially recrystallized structure.

[0050] In a preferred embodiment, the total reduction rate of room temperature cold rolling in step S3 is 20%-60%, and the single-pass reduction rate is 8%-12%. This parameter range ensures sufficient work hardening while taking into account sheet shape quality and edge integrity.

[0051] In a preferred embodiment, the annealing temperature in step S4 is 680-850℃, the holding time is 0.5-8 min, and the cooling rate is 8-12℃ / min. This preferred parameter combination is beneficial for obtaining a heterostructure with a submicron recrystallized grain volume fraction of 40%-60%, achieving optimal strength-plasticity matching.

[0052] In a further preferred embodiment, step S4 is followed by a leveling rolling step: the annealed strip is leveled and rolled with a reduction rate of 0.5%-3%. The purpose of leveling rolling is to eliminate the yield plateau phenomenon formed during annealing, improve the strip shape, and introduce a small number of movable dislocations to improve the initial work hardening ability of the material.

[0053] The high-strength, high-plasticity, multi-scale heterogeneous nanostructured 201 stainless steel obtained by the present invention through the above preparation method has the following microstructure characteristics: (1) Nanoscale deformable lath With a width of 40-550 nm, these deformed laths are mainly distributed in the incompletely recrystallized region. They are formed by the martensitic transformation and shear deformation of austenite during cold rolling, retaining a high density of dislocations and stacking faults, which significantly contribute to strength.

[0054] (2) Submicron-scale recrystallized grains The grains are 0.5-1.5 μm in size and 30%-60% in volume. These grains are formed through recrystallization nucleation and growth during annealing, and have low dislocation density and good plasticity, making them the main carriers for achieving high elongation in materials.

[0055] (3) Micron-sized non-recrystallized grains The grains range in size from 1 to 25 μm and are mainly distributed near the original austenite grain boundaries or coarse second phase. These grains retain the orientation characteristics of the deformed structure and form a grain size gradient with the surrounding submicron grains, resulting in heterogeneous deformation-induced (HDI) strengthening and toughening effects.

[0056] (4) Biphasic matrix structure The matrix consists of 40%–80% austenite and 20%–60% martensite by volume. The austenite phase provides good plasticity and formability, and further contributes to work hardening during deformation through the transformation-induced plasticity (TRIP) effect; the martensite phase provides high strength and work hardening capacity. The synergistic deformation of the two phases effectively delays the occurrence of necking.

[0057] This invention has the following technical advantages: (1) Excellent strong-plasticity matching was achieved. The 201 stainless steel prepared by this invention has a yield strength of 1000-1300 MPa, a tensile strength of 1400-1600 MPa, and a total elongation of 25%-45%. Compared with traditional 201 stainless steel (yield strength approximately 250-500 MPa, total elongation approximately 40%-55%), the yield strength is increased by 2-3 times while maintaining good plasticity; compared with traditional cold-rolled 201 stainless steel (yield strength approximately 1000-1600 MPa, total elongation approximately 10%-20%), the plasticity is significantly improved at the same strength level.

[0058] (2) A unique multi-scale heterogeneous nanostructure was constructed. Through a synergistic thermomechanical treatment of warm rolling-cold rolling-annealing, this invention constructs a multi-scale heterogeneous structure in 201 stainless steel, consisting of nanoscale deformed laths, submicron-scale recrystallized grains, and micron-scale non-recrystallized grains, as well as an austenite / martensite dual-phase matrix. This heterogeneous structure overcomes the inverse relationship between strength and plasticity inherent in traditional single strengthening mechanisms through the synergistic effects of heterogeneous deformation-induced (HDI) strengthening, transformation-induced plasticity (TRIP) effect, grain refinement strengthening, and work hardening.

[0059] (3) The process is simple, the cost is low, and it is easy to industrialize. Compared with high-strength steel containing Co and Mo or processes that require complex large plastic deformation equipment, the warm rolling-cold rolling-annealing process used in this invention is a conventional process in the stainless steel industry. It does not require the addition of expensive alloying elements or the purchase of special equipment, and has good prospects for industrialization.

[0060] (4) It retains the corrosion resistance advantage of 201 stainless steel. This invention does not change the basic chemical composition of 201 stainless steel, and the annealing treatment promotes the uniform distribution of Cr element and the formation of passivation film. Therefore, the material retains the inherent good atmospheric corrosion resistance and weak media corrosion resistance of 201 stainless steel, and is suitable for application scenarios with requirements for corrosion resistance, such as building decoration, home appliances, and rail transportation.

[0061] Example 1 This embodiment provides a multi-scale heterogeneous nanostructured high-strength and high-ductility 201 stainless steel, and the preparation steps are as follows: S1: Hot-rolled 201 stainless steel slabs with a thickness of 4.0 mm (chemical composition: C 0.12%, Ni 1.06%, Cr 13.08%, Mn 9.72%, Si 0.35%, N 0.15%, Cu 0.22%, balance Fe and unavoidable impurities) are solution treated at 1000℃ for 1.0 h and then water quenched to room temperature.

[0062] S2: The solution-treated slab obtained in S1 is heated to 450℃ and subjected to multi-pass warm rolling with a total reduction rate of 35%, a single-pass reduction rate of 15%, a rolling speed of 3.0 m / s, a front tension of 150 MPa, and a back tension of 110 MPa to obtain a warm-rolled strip with a thickness of 2.6 mm.

[0063] S3: The warm-rolled strip obtained in S2 is subjected to multiple cold rolling passes at room temperature, with a total reduction rate of 40% and a single-pass reduction rate of 10%, to obtain a cold-rolled strip with a thickness of 1.6 mm.

[0064] S4: The cold-rolled strip obtained in S3 is annealed at 750°C with a heating rate of 5°C / min and a holding time of 3 min under a N2 protective atmosphere. Then it is cooled to 380°C at a rate of 10°C / min and then air-cooled to room temperature.

[0065] Microstructural characterization: The microstructure of the annealed samples was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The results showed that the material possesses a typical multi-scale heterogeneous structure: nanoscale deformed laths with widths of 40-500 nm and an average width of approximately 255 nm; submicron-sized recrystallized grains with sizes of 0.8-1.0 μm and a volume fraction of approximately 42%; and micron-sized unrecrystallized grains with sizes of 1-22 μm. Figure 1 As shown. XRD and EBSD phase analysis indicate that the matrix consists of 65% austenite and 35% martensite, as shown. Figure 1 and Figure 2 As shown.

[0066] Figure 1 The microstructure of the multi-scale heterogeneous nanostructured high-strength and high-ductility 201 stainless steel prepared in Example 1 of this invention is characterized by SEM-EBSD and HAADF-STEM. Among them, (a) is the inverse pole figure (IPF) distribution map, showing the grain orientation distribution; (b) is the phase distribution map, showing the two-phase distribution of austenite (red) and martensite (green); (c) is the DF-HAADF image, showing the coexistence of nanoscale deformed laths and submicron-scale recrystallized grains, with high-density dislocations inside the laths; (d) is the grain size distribution map, showing the multi-scale grain characteristics.

[0067] Figure 2 The X-ray diffraction (XRD) pattern of the multi-scale heterogeneous nanostructure high-strength and high-plasticity 201 stainless steel prepared in Example 1 of the present invention shows the diffraction peaks of austenite (γ) and martensite (α').

[0068] Mechanical property testing: Standard tensile specimens (gauge length 50 mm, gauge width 12.5 mm) were prepared according to GB / T 228.1 standard. Tensile tests were then performed at room temperature on a universal testing machine at a strain rate of 2.5 × 10⁻⁶. -4 / s. The engineering stress-strain curve is shown below. Figure 3 As shown, the relevant test results are as follows: Table 1 Example 2 This embodiment provides a multi-scale heterogeneous nanostructured high-strength and high-ductility 201 stainless steel, and the preparation steps are as follows: S1: A hot-rolled 201 stainless steel slab with a thickness of 3.0 mm (chemical composition same as in Example 1) was solution treated at 1050°C for 0.5 h, and then water quenched to room temperature.

[0069] S2: The solution-treated slab obtained in S1 is heated to 400℃ and subjected to multi-pass warm rolling with a total reduction rate of 25%, a single-pass reduction rate of 10%, a rolling speed of 1 m / s, a front tension of 100 MPa, and a back tension of 80 MPa to obtain a warm-rolled strip with a thickness of 2.25 mm.

[0070] S3: The warm-rolled strip obtained in S2 is subjected to multiple cold rolling passes at room temperature, with a total reduction rate of 70% and a single-pass reduction rate of 5%, to obtain a cold-rolled strip with a thickness of 0.68 mm.

[0071] S4: The cold-rolled strip obtained in S3 is annealed at 650°C with a heating rate of 5°C / min and a holding time of 10 min under a N2 protective atmosphere. Then it is cooled to 350°C at a rate of 5°C / min and then air-cooled to room temperature.

[0072] Microstructural characterization: Microstructure analysis of the annealed samples was performed using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The results showed that the material possesses a typical multi-scale heterogeneous structure: nanoscale deformed laths with widths ranging from 60 to 400 nm, with an average width of approximately 150 nm; submicron-sized recrystallized grains with sizes ranging from 0.6 to 1.2 μm and a volume fraction of approximately 55%; and micron-sized unrecrystallized grains with sizes ranging from 2 to 18 μm. EBSD phase analysis indicated that the matrix consists of approximately 75% austenite (green) and 25% martensite (red), such as... Figure 5 As shown.

[0073] Standard tensile specimens (gauge length 50 mm, gauge width 12.5 mm) were prepared according to GB / T 228.1 standard. Tensile tests were then performed at room temperature on a universal testing machine at a strain rate of 2.5 × 10⁻⁶. -4 / s. The engineering stress-strain curve is shown below. Figure 3 As shown, the relevant test results are as follows: Table 2 Example 3 This embodiment provides a multi-scale heterogeneous nanostructured high-strength and high-ductility 201 stainless steel, and the preparation steps are as follows: S1: A hot-rolled 201 stainless steel slab with a thickness of 2.5 mm (chemical composition same as in Example 1) was solution treated at 950°C for 2.0 h and then water-quenched to room temperature.

[0074] S2: The solution-treated slab obtained in S1 is heated to 550℃ and subjected to multi-pass warm rolling with a total reduction rate of 50%, a single-pass reduction rate of 20%, a rolling speed of 5 m / s, a front tension of 200 MPa, and a back tension of 150 MPa to obtain a warm-rolled strip with a thickness of 1.25 mm.

[0075] S3: The warm-rolled strip obtained in S2 is subjected to multiple cold rolling passes at room temperature, with a total reduction rate of 15% and a single-pass reduction rate of 15%, to obtain a cold-rolled strip with a thickness of 1.1 mm.

[0076] S4: The cold-rolled strip obtained in S3 is annealed at 950°C with a heating rate of 10°C / min and a holding time of 0.5 min under a N2 protective atmosphere. Then it is cooled to 300°C at a rate of 15°C / min and then air-cooled to room temperature.

[0077] Microstructural characterization: Microstructure analysis of the annealed samples was performed using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The results showed that the material possesses a typical multi-scale heterogeneous structure: nanoscale deformed laths with widths of 50-550 nm and an average width of approximately 210 nm; submicron-scale recrystallized grains with sizes of 0.7-1.3 μm and a volume fraction of approximately 58%; and micron-scale unrecrystallized grains with sizes of 2.5-25 μm. The matrix consists of approximately 80% austenite (green) and 20% martensite (red), such as... Figure 6 As shown.

[0078] Standard tensile specimens (gauge length 50 mm, gauge width 12.5 mm) were prepared according to GB / T 228.1 standard. Tensile tests were then performed at room temperature on a universal testing machine at a strain rate of 2.5 × 10⁻⁶. -4 / s. The engineering stress-strain curve is shown below. Figure 3 As shown, the relevant test results are as follows: Table 3 Example 4 This embodiment provides a multi-scale heterogeneous nanostructured high-strength and high-ductility 201 stainless steel, and the preparation steps are as follows: S1: A 3.0 mm thick hot-rolled 201 stainless steel slab (chemical composition: C 0.16%, Ni 1.30%, Cr 14.21%, Mn 10.57%, Si 0.60%, N 0.19%, Cu 0.77%, balance Fe) was solution treated at 980℃ for 1.5 h and then water quenched to room temperature.

[0079] S2: The solution-treated slab obtained in S1 is heated to 460℃ and subjected to multi-pass warm rolling with a total reduction rate of 40% and a single-pass reduction rate of 12%. The rolling speed is 3 m / s, the front tension is 130 MPa, and the back tension is 100 MPa, to obtain a warm-rolled strip with a thickness of 1.8 mm.

[0080] S3: The warm-rolled strip obtained in S2 is subjected to multiple cold rolling passes at room temperature, with a total reduction rate of 50% and a single-pass reduction rate of 5%, to obtain a cold-rolled strip with a thickness of 0.9 mm.

[0081] S4: The cold-rolled strip obtained in S3 is annealed at 780°C with a heating rate of 6°C / min and a holding time of 2.0 min under a N2 protective atmosphere. Then it is cooled to 350°C at a rate of 8°C / min and then air-cooled to room temperature.

[0082] Microstructural characterization: Microstructure analysis of the annealed samples was performed using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The results showed that the material possesses a typical multi-scale heterogeneous structure: nanoscale deformed laths with widths of 35-450 nm and an average width of approximately 180 nm; submicron-scale recrystallized grains with sizes of 0.5-1.4 μm and a volume fraction of approximately 35%; and micron-scale unrecrystallized grains with sizes of 2-20 μm. The matrix consists of approximately 71% austenite and 29% martensite. Figure 7 As shown.

[0083] Standard tensile specimens (gauge length 50 mm, gauge width 12.5 mm) were prepared according to GB / T 228.1 standard. Tensile tests were then performed at room temperature on a universal testing machine at a strain rate of 2.5 × 10⁻⁶. -4 / s. The engineering stress-strain curve is shown below. Figure 3 As shown, the relevant test results are as follows: Table 4 Example 5 This embodiment provides a multi-scale heterogeneous nanostructured high-strength and high-ductility 201 stainless steel, and the preparation steps are as follows: S1: A hot-rolled 201 stainless steel slab with a thickness of 4.0 mm (chemical composition same as in Example 4) was solution treated at 1020°C for 0.8 h and then water-quenched to room temperature.

[0084] S2: The solution-treated slab obtained in S1 is heated to 430℃ and subjected to multi-pass warm rolling with a total reduction rate of 30%, a single-pass reduction rate of 10%, a rolling speed of 4 m / s, a front tension of 170 MPa, and a back tension of 130 MPa to obtain a warm-rolled strip with a thickness of 2.8 mm.

[0085] S3: The warm-rolled strip obtained in S2 is subjected to multiple cold rolling passes at room temperature, with a total reduction rate of 55% and a single-pass reduction rate of 12%, to obtain a cold-rolled strip with a thickness of 1.3 mm.

[0086] S4: The cold-rolled strip obtained in S3 is annealed at 720°C with a heating rate of 4°C / min and a holding time of 5.0 min under a N2 protective atmosphere. Then it is cooled to 350°C at a rate of 15°C / min and then air-cooled to room temperature.

[0087] S5: The annealed strip is leveled and rolled with a reduction rate of 2.0%.

[0088] Microstructural characterization: Microstructure analysis of the annealed samples was performed using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The results showed that the material possesses a typical multi-scale heterogeneous structure: nanoscale deformed laths with widths of 42-500 nm and an average width of approximately 136 nm; submicron-scale recrystallized grains with sizes of 0.4-1.3 μm and a volume fraction of approximately 31%; and micron-scale unrecrystallized grains with sizes of 2-21 μm. The matrix consists of approximately 74% austenite (green) and 26% martensite (red), such as... Figure 8 As shown.

[0089] Standard tensile specimens (gauge length 50 mm, gauge width 12.5 mm) were prepared according to GB / T 228.1 standard. Tensile tests were then performed at room temperature on a universal testing machine at a strain rate of 2.5 × 10⁻⁶. -4 / s. The engineering stress-strain curve is shown below. Figure 3 As shown, the relevant test results are as follows: Table 5 The flat rolling process in this embodiment eliminates the yield plateau, making the stress-strain curve smoother and facilitating subsequent processing such as stamping.

[0090] Example 6 This embodiment provides a multi-scale heterogeneous nanostructured high-strength and high-ductility 201 stainless steel, and the preparation steps are as follows: S1: A hot-rolled 201 stainless steel slab with a thickness of 4.0 mm (chemical composition same as in Example 4) was solution treated at 990°C for 1.5 h and then water-quenched to room temperature.

[0091] S2: The solution-treated slab obtained in S1 is heated to 500℃ and subjected to multi-pass warm rolling with a total reduction rate of 45% and a single-pass reduction rate of 10%. The rolling speed is 4 m / s, the front tension is 200 MPa, and the back tension is 150 MPa, to obtain a warm-rolled strip with a thickness of 2.2 mm.

[0092] S3: The warm-rolled strip obtained in S2 is subjected to multiple cold rolling passes at room temperature, with a total reduction rate of 30% and a single-pass reduction rate of 10%, to obtain a cold-rolled strip with a thickness of 1.54 mm.

[0093] S4: The cold-rolled strip obtained in S3 is annealed at 850°C with a heating rate of 10°C / min and a holding time of 1.0 min under a N2 protective atmosphere. Then it is cooled to 350°C at a rate of 15°C / min and then air-cooled to room temperature.

[0094] Microstructural characterization: The microstructure of the annealed samples was analyzed using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results showed that the material possesses a typical multi-scale heterogeneous structure, such as... Figure 9 As shown.

[0095] Standard tensile specimens (gauge length 50 mm, gauge width 12.5 mm) were prepared according to GB / T 228.1 standard. Tensile tests were then performed at room temperature on a universal testing machine at a strain rate of 2.5 × 10⁻⁶. -4 / s. The engineering stress-strain curve is shown below. Figure 3 As shown, the relevant test results are as follows: Table 6 Example 7 This embodiment provides a multi-scale heterogeneous nanostructured high-strength and high-ductility 201 stainless steel, and the preparation steps are as follows: S1: A hot-rolled 201 stainless steel slab with a thickness of 4.0 mm (chemical composition same as in Example 4) was solution treated at 960°C for 1.8 h and then water-quenched to room temperature.

[0096] S2: The solution-treated slab obtained in S1 is heated to 520℃ and subjected to multi-pass warm rolling with a total reduction rate of 35%, a single-pass reduction rate of 16%, a rolling speed of 2m / s, a front tension of 100 MPa, and a back tension of 80 MPa to obtain a warm-rolled strip with a thickness of 2.6 mm.

[0097] S3: The warm-rolled strip obtained in S2 is subjected to multiple cold rolling passes at room temperature, with a total reduction rate of 45% and a single-pass reduction rate of 5%, to obtain a cold-rolled strip with a thickness of 1.43 mm.

[0098] S4: The cold-rolled strip obtained in S3 is annealed at 680°C with a heating rate of 7°C / min and a holding time of 8.0 min under a N2 protective atmosphere. Then it is cooled to 350°C at a rate of 6°C / min and then air-cooled to room temperature.

[0099] Microstructural characterization: The microstructure of the annealed samples was analyzed using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results showed that the material possesses a typical multi-scale heterogeneous structure, such as... Figure 10 As shown.

[0100] Standard tensile specimens (gauge length 50 mm, gauge width 12.5 mm) were prepared according to GB / T 228.1 standard. Tensile tests were then performed at room temperature on a universal testing machine at a strain rate of 2.5 × 10⁻⁶. -4 / s. The engineering stress-strain curve is shown below. Figure 3 As shown, the relevant test results are as follows: Table 7 Example 8 This embodiment provides a multi-scale heterogeneous nanostructured high-strength and high-ductility 201 stainless steel, and the preparation steps are as follows: S1: A hot-rolled 201 stainless steel slab with a thickness of 3.0 mm (chemical composition same as in Example 4) was solution treated at 1010°C for 1.0 h and then water-quenched to room temperature.

[0101] S2: The solution-treated slab obtained in S1 is heated to 470℃ and subjected to multi-pass warm rolling with a total reduction rate of 38%, a single-pass reduction rate of 13%, a rolling speed of 4 m / s, a front tension of 160 MPa, and a back tension of 120 MPa to obtain a warm-rolled strip with a thickness of 2.48 mm.

[0102] S3: The warm-rolled strip obtained in S2 is subjected to multiple cold rolling passes at room temperature, with a total reduction rate of 48% and a single-pass reduction rate of 9%, to obtain a cold-rolled strip with a thickness of 1.3 mm.

[0103] S4: The cold-rolled strip obtained in S3 is annealed at 800℃ with a heating rate of 5℃ / min and a holding time of 1.5 min under N2 protective atmosphere. Then it is cooled to 350℃ at a rate of 10℃ / min and then air-cooled to room temperature.

[0104] S5: The annealed strip is leveled and rolled with a reduction rate of 1.5%.

[0105] Microstructural characterization: The microstructure of the annealed samples was analyzed using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results showed that the material possesses a typical multi-scale heterogeneous structure, such as... Figure 11 As shown.

[0106] Standard tensile specimens (gauge length 50 mm, gauge width 12.5 mm) were prepared according to GB / T 228.1 standard. Tensile tests were then performed at room temperature on a universal testing machine at a strain rate of 2.5 × 10⁻⁶. -4 / s. The engineering stress-strain curve is shown below. Figure 3 As shown, the relevant test results are as follows: Table 8 Comparative Example 1: Conventionally Solution-Treated 201 Stainless Steel A 3.0 mm thick hot-rolled 201 stainless steel slab (chemical composition same as in Example 1) was solution treated at 1050°C for 1 h and then water-quenched to room temperature. No subsequent deformation or annealing treatment was performed.

[0107] Microstructure: Equiaxed austenitic grains, with an average grain size of approximately 25 μm.

[0108] Standard tensile specimens (gauge length 50 mm, gauge width 12.5 mm) were prepared according to GB / T 228.1 standard. Tensile tests were then performed at room temperature on a universal testing machine at a strain rate of 2.5 × 10⁻⁶. -4 / s. The engineering stress-strain curve is shown below. Figure 3 As shown, the relevant test results are as follows: Table 9 Compared with Examples 1-8, traditional solution-treated 201 stainless steel has excellent plasticity but extremely low strength, making it difficult to meet structural load-bearing requirements.

[0109] Comparative Example 2: Conventional cold-rolled 201 stainless steel A hot-rolled 201 stainless steel slab with a thickness of 3.0 mm (chemical composition same as in Example 1) was directly subjected to room temperature cold rolling with a total reduction rate of 40% and a single-pass reduction rate of 10% to obtain a cold-rolled strip with a thickness of 1.8 mm.

[0110] Microstructure: deformable texture and banded structure.

[0111] Standard tensile specimens (gauge length 50 mm, gauge width 12.5 mm) were prepared according to GB / T 228.1 standard. Tensile tests were then performed at room temperature on a universal testing machine at a strain rate of 2.5 × 10⁻⁶. -4 / s. The engineering stress-strain curve is shown below. Figure 3 As shown, the relevant test results are as follows: Table 10 Comparative Example 3: Conventional cold-rolled 201 stainless steel A hot-rolled 201 stainless steel slab with a thickness of 3.0 mm (chemical composition same as in Example 1) was directly subjected to room temperature cold rolling with a total reduction rate of 60% and a single-pass reduction rate of 10% to obtain a cold-rolled strip with a thickness of 1.2 mm.

[0112] Microstructure: deformable texture and banded structure.

[0113] Table 11 Compared with Examples 1-8, although the traditional cold rolling process improves the strength through work hardening, it suffers severe loss of plasticity and fails to form the multi-scale heterogeneous structure of the present invention, resulting in poor strength-plasticity matching.

[0114] Comparative Example 4: The warm rolling step is omitted (cold rolling is performed directly after solution treatment). S1: A hot-rolled 201 stainless steel slab with a thickness of 4.0 mm (chemical composition same as in Example 1) was solution treated at 1000℃ for 1.0 h and then water quenched to room temperature.

[0115] S2: The solution-treated slab obtained in S1 is subjected to multiple cold rolling passes at room temperature, with a total reduction rate of 65% and a single-pass reduction rate of 10%, to obtain a cold-rolled strip with a thickness of 1.4 mm.

[0116] S3: The cold-rolled strip obtained in S2 is annealed at 750°C with a heating rate of 5°C / min and a holding time of 3 min under a N2 protective atmosphere. Then it is cooled to 380°C at a rate of 10°C / min and then air-cooled to room temperature.

[0117] Microstructural characterization: The microstructure of the annealed samples was analyzed using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results showed that the samples consisted of coarse, elongated austenite (green) and martensite (red) grains distributed along the rolling direction, surrounded by fine austenite and martensite grains. The grain size distribution after annealing exhibited a bimodal characteristic. Figure 12 As shown, Comparative Example 4 lacks warm rolling pretreatment, making it prone to local dislocation pile-up during cold rolling deformation, resulting in uneven dislocation distribution and the absence of fine initial deformed grains obtained through warm rolling. Furthermore, it cannot form the nano-submicron-micron multi-scale synergistic heterostructure of this invention after annealing.

[0118] Standard tensile specimens (gauge length 50 mm, gauge width 12.5 mm) were prepared according to GB / T 228.1 standard. Tensile tests were then performed at room temperature on a universal testing machine at a strain rate of 2.5 × 10⁻⁶. -4 / s. The engineering stress-strain curve is shown below. Figure 3 As shown, the relevant test results are as follows: Table 12 Compared with Example 1, the lack of a warm rolling step resulted in poor microstructure uniformity, uncontrollable recrystallization behavior after annealing, and poor strength-plasticity matching.

[0119] In summary, comparing Examples 1-8 with Comparative Examples 1-4, it is evident that the introduction of a warm rolling process is a crucial prerequisite for the formation of multi-scale heterogeneous structures. Within the temperature range of 400-550℃, 201 stainless steel is in a critical state of dynamic recovery and partial dynamic recrystallization. This "incomplete recrystallization" microstructure lays the foundation for the formation of heterogeneous grain structures during subsequent room temperature cold rolling and annealing. Furthermore, the annealing temperature and time directly determine the degree of recrystallization and the formation of multi-scale structures. Within the range of 650-950℃, by controlling the heating rate, holding time, and cooling rate, precise control of the recrystallized grain size, volume fraction, and phase composition can be achieved, thereby obtaining the optimal balance between strength and plasticity.

[0120] Examples 1-8 of this invention all employ conventional equipment (hot rolling mill, cold rolling mill, annealing furnace) and conventional processes used in the stainless steel industry, requiring no additional expensive alloying elements or the purchase of specialized equipment. The leveling rolling step in Examples 5 and 8 further improves the sheet shape and surface quality, which is beneficial for subsequent stamping and forming processes.

[0121] In the multi-scale heterogeneous nanostructured 201 stainless steel prepared by this invention, nanoscale deformable laths provide high strength, submicron-scale recrystallized grains provide good plasticity, and micron-scale unrecrystallized grains form a grain size gradient with the surrounding fine grains, generating heterogeneous deformation-induced (HDI) stress and promoting work hardening. The austenite / martensite dual-phase matrix contributes to plasticity synergistically through the TRIP effect and dislocation multiplication during deformation. This multi-mechanism synergistic effect breaks through the traditional inverse relationship between strength and plasticity based on a single strengthening mechanism.

[0122] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing high-strength, high-ductility 201 stainless steel with a multi-scale heterogeneous nanostructure, characterized in that, Includes the following steps: S1. The hot-rolled 201 stainless steel slab is solution treated and then water-quenched to room temperature. S2. The solution-treated slab obtained in step S1 is subjected to multi-pass warm rolling at 400-550℃, with a total reduction rate of 25%-50% and a single-pass reduction rate of 10%-20%, to obtain warm-rolled strip. S3. The warm-rolled strip obtained in step S2 is subjected to room temperature multi-pass cold rolling with a total reduction rate of 15%-70% and a single-pass reduction rate of 5%-15% to obtain cold-rolled strip. S4. The cold-rolled strip obtained in step S3 is annealed at 650-950℃ for 0.5-10 min under a protective atmosphere at a heating rate of 3-10℃ / min, then cooled to below 400℃ at a cooling rate of 5-15℃ / min, and then air-cooled to room temperature to obtain the multi-scale heterogeneous nanostructured high-strength and high-plasticity 201 stainless steel.

2. The preparation method according to claim 1, characterized in that, In step S1, the solution treatment temperature is 950-1050℃ and the time is 0.5-2 h.

3. The preparation method according to claim 1, characterized in that, In step S1, the chemical composition of the 201 stainless steel plate, by mass percentage, includes: C<0.2%, Ni 1.0%-2.0%, Cr 12.5%-15.5%, Mn 8.0%-11.0%, Si <0.75%, N<0.2%, Cu <1.0%, with the balance being Fe and unavoidable impurities.

4. The preparation method according to claim 1, characterized in that, In step S2, the rolling speed of the multi-pass warm rolling is 1-5 m / s, and the rolling process uses a front tension of 100-200 MPa and a back tension of 80-150 MPa.

5. The preparation method according to claim 1, characterized in that, Step S4 is followed by a step of leveling and rolling the strip obtained after annealing; the reduction rate of the leveling and rolling is 0.5%-3%.

6. The preparation method according to claim 1, characterized in that, In step S2, the temperature of the multi-pass warm rolling is 420-480℃, and the single-pass reduction rate is 12%-18%; in step S3, the total reduction rate of the room temperature multi-pass cold rolling is 20%-60%, and the single-pass reduction rate is 8%-12%.

7. The preparation method according to claim 1, characterized in that, In step S4, the annealing temperature is 680-850℃, the time is 0.5-8 min, and the cooling rate is 8-12℃ / min.

8. The high-strength, high-ductility 201 stainless steel with multi-scale heterogeneous nanostructure prepared by the preparation method according to any one of claims 1-7.

9. The high-strength, high-ductility 201 stainless steel with a multi-scale heterogeneous nanostructure according to claim 8, characterized in that, The matrix consists of 40%-80% austenite and 20%-60% martensite by volume, and has the following multi-scale heterogeneous nanostructure: Nanoscale deformable slats with widths of 40-550 nm; Submicron-sized recrystallized grains, with a size of 0.5-1.5 μm and a volume fraction of 30%-60%; Micron-sized, non-recrystallized grains, ranging in size from 1 to 25 μm.

10. The high-strength, high-ductility 201 stainless steel with a multi-scale heterogeneous nanostructure according to claim 8, characterized in that, The yield strength is 1000-1300 MPa, the tensile strength is 1400-1600 MPa, and the total elongation is 25%-45%.

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